In San Diego County, Republican Rep. Duncan Hunter survived the election despite facing corruption charges. A 60-count federal grand jury indictment against him and his wife alleges the couple illegally used $250,000 in campaign funds for vacations, meals and other personal expenses.

Levin's victory carries symbolic weight because of Issa's nearly two-decade tenure, during which he was a chief antagonist of President Barack Obama. The 49th District is partly in the one-time GOP stronghold of Orange County. The rest is in San Diego County.

Levin, an environmental attorney, had about 54 percent of nearly 177,000 votes counted so far.

He sparred with Republican rival Diane Harkey over President Donald Trump's agenda, global warming and immigration. Harkey, a former state lawmaker, had been endorsed by the president.

"I don't think that the traditional Orange County Republican embraces Trumpism," Levin told The Associated Press. He said voters in the district are concerned with coastal protection and climate change.

Issa's district was among seven in the state that were carried by Hillary Clinton in the 2016 presidential election. Democrats saw all as potential pickups this November.

The battlegrounds range from Central Valley farmland to legendary surfing spots in Orange County and Knight's 25th District, which cuts through suburbs, horse ranches and high desert in northern Los Angeles County and a small slice of Ventura County.

Knight trailed Hill by 2.5 points with about 163,000 votes counted and thousands more left to be tallied. The Associated Press has not called the race.

Knight, a former police officer, offered Hill his congratulations and said he was proud of his work on veterans' health care, small business development and defense issues.

"Our electoral process is integral to our identity as a free and fair society, and the voters have spoken," he said.

Hill stressed her centrist politics: She's a gun owner and her Republican father is a police officer who had never voted for a Democrat before her primary. Her mother, a Democrat, is a nurse.

"I look forward to working on behalf of everyone in this district to ensure we all have access to quality health care, housing we can afford, and a representative and transparent government which truly serves the people," she said.

Republican Reps. Mimi Walters and Dana Rohrabacher were fighting for their political lives in two Orange County districts they easily won two years ago.

In the 45th District, which has a 7-point GOP registration edge, Walters was leading law professor Katie Porter, a protégé of Massachusetts Democratic Sen. Elizabeth Warren, by about 3 points with 184,000 votes counted.

Porter had campaigned on overturning Trump's tax reform package and her support for universal health care.

Rohrabacher, known as Russia's leading defender on Capitol Hill, was in a tough race with Republican-turned-Democrat Harley Rouda in the 48th District, where the GOP has a 10-point registration edge.

Rouda, a real estate executive, has depicted the 15-term congressman as the face of Washington gridlock. He was leading with 51 percent of the vote, with about 181,000 counted.

In retiring GOP Rep. Ed Royce's 39th District that includes part of Orange County, Republican Young Kim held a 3-point edge over Democrat Gil Cisneros, with about 150,000 votes counted. If elected, Kim would become the first Korean-American immigrant woman elected to the House.

The former state legislator worked for Royce for years and has positioned herself as a Trump supporter with an independent streak.

Cisneros, a first-time candidate who won a $266 million lottery jackpot, was looking for a big turnout from Hispanics who make up about a third of the population.

Two other targeted Republicans, Reps. David Valadao and Jeff Denham, represent farm-belt districts where Democrats have more registered voters but are more moderate than in urban areas.

Valadao's 21st District includes parts of Fresno, Kern, Kings and Tulare counties. He won by a wide margin in 2016 and on Tuesday held off a challenge by Democrat T.J. Cox.

Cox tried to make the race a referendum on Valadao's support for President Donald Trump. In a tip to the district's heavy Hispanic population, Valadao touted his support for a way to keep in the country people who came as children when their parents illegally entered.

In the 10th District, anchored in Modesto, Denham was leading Democrat Josh Harder by about 1,300 votes point with 112,000 votes counted.

Harder argued that Republican policies in Washington have hurt many residents. He emphasized that Denham voted to repeal the Affordable Care Act, which Harder supports.

Denham, known for his involvement in water issues vital to agriculture, has proven tough to beat, despite the Democratic registration edge. He won by 3 percentage points in 2016.

Representing a district with a large Hispanic population, Denham has pushed for Congress to consider a pathway for citizenship for hundreds of thousands of immigrants who came to the U.S. as children and stayed here illegally.